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RADIUS

HauteSaoneFrance

Joined: 2-01-14

Topics: 27

Replies: 91

Posted: Sat 1st Nov 2014, 3:11pm
RADIUS

Only just started learning, nothing practical has happened yet on my proposed garden railway but mostly on my mind are gradients and radiuses, my question on the former seems to have been answered in that a 1 in 25 gradient is possible. On my thread a 'A Very Steep Gradient' contributors are mentioning radiuses of 4 and 6 metres. What is a reasonable minimum in my case I have a locomotive yet to run on any track, it's an 0-4-0 with a I/2 metre (20 inch) wheelbase, the tender is less and bogies to be used for rolling stock have 11 inch wheel centres. Is there a recommended 'standard' application that can be used for wheelbase to radius correlation? Although part of my site will allow for generous radiuses of up to 17m other parts can only be used if much lesser radiuses are possible
 

Replies To This Post

Xz

Joined: 1-01-92

Topics: 17

Replies: 244

Posted: Sat 1st Nov 2014, 7:12pm

Another, how long is a piece of string question. Radius' should always be kept as large as possible. With a 20" wheelbase I wouldn't expect much less than 4m, in fact that may be pushing it. There are other factors that need to be considered including wheel diameter. A small wheel will fair better at the limits than a large one. Suck it and see!
 

George Coles

Joined: 4-08-09

Topics: 19

Replies: 90

Posted: Sat 1st Nov 2014, 7:44pm

In the recent past, in 'The News', there was an article on this subject.
It included a formula for determining minimum radius, as follows:-
R(min)=W sqrt(f(d+f))/P
where:
W= overall wheelbase
f=flange depth
d=dia of wheel on tread
P=sideplay between flange and track gauge
NB sqrt =square root!
for 7.25" standards the following are appropriate
f=0.188"
P=0.125"


Hope this helps

George C
 

Peter Beevers

Joined: 9-10-01

Topics: 3

Replies: 134

Posted: Sat 1st Nov 2014, 9:49pm

The rule of thumb many people use is 20 times the longest fixed wheelbase, and that will need a little gauge widening. At slow speed, with more gauge widening, you can get away with tighter radii.
 

Railrose

Joined: 25-06-07

Topics: 1

Replies: 8

Posted: Thu 6th Nov 2014, 12:40am

I built a large portable layout system with a standard 6 feet/ 180 cm radius. 2 mm gauge widening, all tracks are on 186 mm, straight ones too for easy connection. My 0-4-0 petrol mechanic has a 1/2 metre/20" wheelbase and 130mm dia wheels. 250 meters of track with 14 switces including a single and double slip. No problem even with longer trains.

However with those tighter radii regular greasing is necessary.

6 feet radius isn't the limit, I run indoors on a 3 (three) feet radius, with 5 mm gauge widening. No problem with 18" wheelbase and 4"dia wheels. Tighter even must be possible but I haven't yet found the time to try.

More pictures in Rosie's Railroad Adventures in The News
I built a large portable layout system with a standard 6 feet/ 180 cm radius. 2 mm gauge widening, all tracks are on 186 mm, straight ones too for easy connection. My 0-4-0 petrol mechanic has a 1/2 metre/20" wheelbase and 130mm dia wheels. 250 meters of track with 14 switces including a single and double slip. No problem even with longer trains.

However with those tighter radii regular greasing is necessary.

6 feet radius isn't the limit, I run indoors on a 3 (three) feet radius, with 5 mm gauge widening. No problem with 18" wheelbase and 4"dia wheels. Tighter even must be possible but I haven't yet found the time to try.

More pictures in Rosie's Railroad Adventures in The News
 
 
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